16 Comments

Could a coronal mass ejection be responsible for this?The sensor probably does interface with grid power. A sensor has to connect to the equipment it is being used for so there is very probably an electrical connection and it is probably actually powered by the equipment it is connected to. Sensors usually aren't self powered.

Could an ultra-relativistic particle tunnel directly through a stellar mass black hole?I'm not getting why the cross-sectional area of the horizon matters. We are talking about the probability of the particle tunnelling through a thin potential barrier. The size of the barrier in the directions perpendicular to the direction of motion would seem to be irrelevant. To put it another way - if I were to replace the black hole with a normal matter wall, how would that differ for the question of tunnelling a ultra-relativistic particle through it?

Is there a named unit that, when divided by 32, gives meters per second?It sounds like someone got a meters to feet conversion backwards. 10 meters is about 32.8 feet. Also, are you getting meters per second (velocity) or meters per second squared (acceleration)? 1 g is about 9.8 meters/(secsec) or 32.1 feet/(secsec). Another context where 32 shows up is in atmospheres of pressure. You get about 1 atmosphere of pressure for a water column 32 feet deep. Context would help a lot in guessing why 32 is showing up.

Apr6

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Why does a coin falls faster when it's flipping as well?To extend on my remark about the difference in the fall distance of the center of mass: A difference of only 1.1 millimeters in the fall distance would change the fall time by 15 milliseconds. That is on the order of the thickness of a typical small coin.

Apr6

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Why does a coin falls faster when it's flipping as well?You need to specify your experimental setup better. I can think of a few things that could be causing issues such as differences between the location and fall distances of the center of mass of the coin when dropped to make it flip vice dropped to not flip. You could be accidentally be effectively dropping the 'flipping' coin a shorter distance. You could also be having air flow effects caused by a nearby surface as the coin rotates. There are several possible sources of the difference, but they depend on your setup.

How do levers amplify forces?Here is a mental model that might help. Think of a series of balls connected in a straight line by very rigid springs floating in space with no external forces acting on it. When it is in its 'rest state' there are no stresses on it. Now give the ball at one end of the assembly a push at right angles from the line. When you do that the spring connecting it to the next ball bends a bit - transmitting the force to the next ball as it tries to straighten out the line. From there to the next ball, and so on.

Equivalence principle and radiation from falling particleDon't think about it from an energetic argument. Think about it from the perspectives of what the time evolution of the electric field looks like in the co-moving frame of reference and then from the laboratory frame of reference.

Feb25

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Keeping air in a wellThis is equivalent to constructing a shell around a planet at some arbitrary altitude. The pressure at the bottom of your hole will remain steady as long as the air pressure at the top is the same as the 'natural' pressure for that altitude.By which I mean if you start with some global specific (low) pressure at the top before you start digging, the pressure at the bottom of the hole will simply be the pressure you would get if the atmosphere was as much thicker as your hole is deep.

Feb16

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Why does a window become a mirror at night?The adjustment of pupil size is only a small part of the story (it accounts for perhaps a factor of 10 in the overall sensitivity). The eye actually becomes more and less sensitive by a much larger factor via other mechanisms. It is more akin to turning up and down the gain of the retina itself.